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Issued December 1942 STAtp^' E " 5P ^ 

Revised July 1946 ° iAr£ PLANT BGARO 

United States Department of Agriculture 
Agricultural Research Administration 
Bureau of Entomology and Plant Quarantine 


Prepared by the Division of Bee Culture 


The principal role of the honeybee is not in the production of honey 
and beeswax, as is commonly supposed, but in the pollination of agricul- 
tural crops for the production of seed and fruit. Without insects to 
effect pollination, many species of plants will not set seed or produce 
fruit no matter how well they are cultivated, fertilized, and protected 
from diseases and pests. 

Although the honeybee is the most important pollinating insect, it 
is but one of many species of bees necessary for the perpetuation of 
flowering plants. Various species of flies, beetles, and other insects 
also visit flowers and to some extent pollinate them. Whereas nectar and 
pollen are rarely the principal food of other pollinating insects, these 
substances supply the entire nourishment of both the young and adults of 
honeybees and wild bees. 

Wherever a proper balance exists between plants and pollinating in- 
sects, both flourish. Agricultural development, however, has seriously 
interfered with this balance. It has demanded the growing of certain 
plants in enormous acreages and has unwittingly destroyed native pollina- 
ting insects as well as their nesting places. As a result the burden of 
pollination has been increased to such an extent that wild bees are no 
longer adequate or dependable, particularly where agriculture is highly 
developed. In many places the depletion of wild pollinators is so acute 
that honeybees have to be brought in especially for pollination, and so 
in practically all agricultural areas honeybees are now the most numerous 
of the flower-visiting insects. It is essential, nevertheless, to con- 
serve our native pollinating insects, since some species of native bees 
are more efficient, bee for bee, than honeybees and will work under more 
adverse conditions. As yet, however, no agency, Federal, State or private, 
has assumed the responsibility for conserving wild pollinating insects. 

The reduction in wild beneficial insects and the increase in acreage 
of crops requiring insect pollination have been gradual. While these 
changes were occurring, commercial beekeeping had its inception and fortu- 
nately so, since the presence of honeybees in some areas has helped to make 

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up the shortage of wild pollinators. Consequently, plant growers and 
farmers generally have not been greatly concerned about pollination 
simply because some beekeeper has relieved them of this worry by keeping 
his bees within flight range of their crops. 

The service rendered to agriculture by the beekeeper in furnishing 
the public with pollinating insects has commonly been overlooked. In 
too many cases his only reward has been his honey crop, which, until war 
years, he often had to dispose of at depressed prices. In addition, his 
bees were frequently killed through the indiscriminate use of insecticides 
by the very man he was benefiting. Under such circumstances, since the 
beekeeper's interest was not safeguarded by sufficiently high honey prices, 
rentals, or a subsidy of any kind, the keeping of bees has declined in 
many communities, and this in turn has meant decreased yields for the 
grower of insect-pollinated crops. 

The fertilization of flowers is so imperative that beekeeping must 
be carried on to maintain a profitable agriculture. Cwing to conditions 
brought about by the recent war, of which increased acreage of i?isect- 
pollinated seed crops is but one, safeguarding the beekeeping industry 
has become doubly urgent. Beekeeping can be mastered only through years 
of experience. It cannot be learned as a trade is learned, and there is 
no floating population of persons seeking employment in beekeeping. The 
fact that bees have a propensity for stinging discourages many people 
from keeping them, and only certain individuals possess the proper tempera- 
ment to be beekeepers. For these reasons every experienced beekeeper should 
be encouraged to continue with his bees. It may even become necessary to 
subsidize the keeping of bees, since there is no practical substitute 
for honeybees in the transfer of pollen from flower to flower and from 
plant to plant. 

- 3 - 

In the following pages literature is cited in support of the premise 
(1) that wild pollinating insects are deficient in number adequately to 
pollinate our agricultural crops, and (2) that at least 50 agricultural 
crops depend upon honeybees for pollination or yield more abundantly when 
bees are plentiful. 1/ The specific fruit and seed crops mentioned in 
these references are tabulated below: 



Seed Crops 











Brussels sprouts 





Blueberry and huckleberry 













Clovers (alsike, 




red, strawberry, white, 



and Ladino white) 

Sweet clover 


Collar ds 





Peach and nectarine 






Persimmon , 



Plum and prune 






Fletcher, S. W. 

1941. Pollination. Standard cyclopedia of horticulture, by 
L. H. Bailey, v. 3, pp. 2734-2737. New York 

p. 2734 J is well known that while the flowers of many 
plants may be readily fertilized by their own pollen, the offspring 
are stronger when pollen from another plant or another variety has 
had access to the flower. Sometimes pollen from a foreign variety 

1/ These quotations are for the most part from plant specialists, 
with only a few from authorities on apiculture. 

2/ The underlining in the references does not appear in the original 
citations but has been added for emphasis. 

- 4. - 

is absolutely essential to the best fruit-formation. This is particu- 
larly true of certain varieties of the pear. A poor quality of fruit 
can be prevented only by growing together different varieties. Again, 
although a plant may readily pollinate itself, yet the pollen from 
another plant or variety may be prepotent over its own. This is to 
say, if the plant be pollinated by its own pollen along with that of 
a foreign variety, that of the foreign variety will usually effect 
fertilization . 

pp. 2734-5: The flowers of insect-pollinated plants, on the 
other hand, are usually showy, and have nectar or fragrance, or both. 
The pollen is more or less moist or sticky, so that it is not easily 
blown away... As the insect reaches down for the nectar, which is near 
the bottom of the flower, some parts of its body are sure to become 
dusted with pollen... Thus cross-pollination, or the transfer of pollen 
from the anthers of one flower to the pistil of another, is accomplished. 

[Bees collecting pollen are Just as valuable as those gathering nectar. 
In visiting large flowers they may be more effective, as they go directly 
to the reproductive organs.] 

The value of crossing to plants was first clearly proved by 
Charles Darwin in 1859... From the observations of Kolreuter, Sprengel, 
Knight, and his own exhaustive experiments, Darwin showed that co n- 
tinued self-fertilization is likely to result in Inferior offspring ; 
while cross-fertilization, within certain limits, gives greater vigor 
to the offspring. Cross-fertilization between different flowers on 
the same plant usually has no appreciable advantage. 

p. 2736: In the selection of a pollinizer, several points 
must be considered: (1) The two sorts must blossom approximately at 
the same time in order that cross-pollination may be possible. The 
transfer of pollen from one variety to another is performed mainly by 
insects. Waugh and Backhouse have shown that practically none of the 
pollen of the plum and other stone-fruits is carried by wind, it being 
moist and sticky. The same is true of pears, but apple pollen is 
somewhat drier and is wind-blown to a slight extent. The honeybee is 
the most important pollen-carrier. Hooper estimates that in England 
30 per cent of the cross-pollinaticr. is done by the hive bee. 15 per 
cent by various wild bees, especially the bumble-bee, and 5 per cent 
by miscellaneous insects . 

llf this was true for England with its large areas devoted to hedge- 
rows, woods, and small-scale farming with many wild areas suitable for 
the nesting of native bees, then in this country with its large blocks of 
clean cultivation, dwindling wild areas, its large sheep population and 
much greater use of arsenicals, the percentage of pollination effected by 
the honeybee must be even higher.] 

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pp, 2736-7: Orchard pollination, however, is a broader 
problem than the mere detection of varieties that are inclined to be 
unfruitful when planted alone, and discovering which are the best 
pollinizers for each of them. Experiments in crossing and observa- 
tions in orchards indicate that nearly all varieties, whether self- 
sterile or self -fertile, will produce more or better fruit with 
foreign poll en than with their own . . . Tellow Newtown is distinctly 
self -fertile in Oregon, yet Lewis noted a decided improvement in the 
fruit when Jonathan and Grimes* pollen was used upon it. He concluded, 
" All varieties of pome-f ruits , at least of apples and pears P even 
though they may be termed self-fertile, are benefited by having other 
varieties planted with them as polHnizers .* 

IA survey of the literature shows that the last statement is not 
confined to fruit but is applicable to many agricultural crops as well.] 

MacDaniels, L. H. 

1929. Pollination studies in New York State. Amer. Soc. Hort. Sci. 

Proc. .1928 1 129-137. 

p. 137i The value of having bees and good pollen varieties 
in the orchard is that in some seasons when there are only a few 
hours in which bees can fly, satisfactory cross-pollination will be 
effected whereas it would not have been accomplished if sources of 
good pollen and abundant insects were not close at hand. It is for 
such minimum conditions for cross-pollination that the grower should 
provide. It is also evident that in any region the lack of pollen 
carriers in the orchard at blooming time may be the limiting factor 
in the set of fruit and that in order to properly understand the 
pollination problem a study of the insects of the locality in their 
relation to pollination is necessary . 

MacDaniels, L. H. 

1930. Practical aspects of the pollination problem. N. Y. State Hort. 

Soc. Proc. 1930: 195-202. 

p. 201: In the foregoing paragraphs much has been said of 
the limitations of bees in pollen distribution. It must be borne in 
mind, however, that for all that, bees are still the most effective 
pollen carriers there are and that they are the only insect that can 
h« mAnfprn^ h y the orchardist . 

Marshall, R. E., Johnston, Stanley, Hootman, H. D., and Wells, H. M. 
1929. Pollination of orchard fruits in Michigan. Mich. Agr. Expt. 
Sta. Spec. Bui. 188, 38 pp. 

P» 38: The commercial fruit grower is almost entirely depend- 
ent on the common honey bee for the transfer of pollen from one varie- 
ty to another . 

- 6 - 

There are not enough bees in many orchards to insure the 
setting of a full crop of fruit in years when weather conditions are 
not favorable for maximum insect activity at blooming time. 


Authorities universally admit the importance of wild insects in 
pollinating agricultural crops; yet no State or Federal organization is 
especially concerned with the conservation of beneficial insects. It is 
apparent, therefore, that the destruction of pollinating insects has not 
been fully recognised as the important cause of decreased seed and fruit 
production in many crops that are benefited by insect pollination. 

In considering the part played by wild pollinating insects, it should 
be borne in mind that most species, with the exception of bumblebees, are 
solitary insects and reproduce slowly, and since the females have to fly 
in search of food they are subjected to such hazards as weather, fast- 
moving automobiles, natural enemies, etc. Many of the solitary bees are 
ground-nesting and are consequently easily destroyed in areas where agri- 
cultural practices demand frequent cultivation of the soil. 

Certain species of flies, beetles, and other insects effect pollina- 
tion but are considered of minor importance. 

Megee, C. R., and Kelty, R. M. 

1932. The influence of bees upon clover and alfalfa seed production. 
Mich. Agr. Expt. Sta. Quart. Bui. Us 271-277. 

p. 271: It is common observation that along with the 
decrease in the numbers of bumble bees and other wild bees there has 
been a decrease in the production of clover seed. 

p. 277: Bumble bees are effective pollinating agents, but, 
due to their relative scarcity in the clover and alfalfa seed pro- 
ducing districts of northern Michigan cannot be depended on for 
pollination purposes. 

Metcalf, C. L., and Flint, W. P. 

1928. Destructive and useful insectsj their habits and control. 
918 pp. New York. 

p. 264: Under farming conditions great changes take place in 
the character of the plants grown on the land . There are no longer 
a great number of species, generally intermixed, but a few species 
occupying the land in nearly pure stands of thousands and hundreds 
of thousands of acres. This affects the insect population of the 
land in two general ways. Many of those which depend on the plants 
of one family, or even on one species of plant, find their food supply 

- 7 - 

cut off, except in the small uncultivated areas and may nearly, or 
quit e, disappear from the region , as certain species of the billbugs 
in drained bottom lands. 

Vans ell, 0. H. 

1942. Factors affecting the usefulness of honeybees in pollination. 
U. S. Dept. Agr. Cir. 650, 31 pp. 

p. 2: The orchards were located on top of a ridpe, which was 
flanked on both sides by uncultivated lands, including both timber 
and manzanita-ceanothus brush. 

pp. $-6: In the Camino district honeybees were the most 
common visitors to the blossoms , blowflies were next,- and other in- 
sects were scarce . As a rule honeybees visit the blossoms of only 
one plant species on each field trip, while most other insects fre- 
quently shift from one species to another. For this reason no other 
insect compares favorably with the honeybee in pollen-distributing 
activity. Only honeybees and wild bees collected pollen for removal 
to their nests . Ants were surprisingly common in the orchard blos- 
soms, feeding on nectar at temperatures well below that at which fly- 
ing insects cease activity. Ants were observed working in early 
morning, late evening, and during cold rainy periods, but probably 
they do not often move from tree to tree. Pollen seemed to offer no 
special attraction to them, but nectar and possibly sap did, because 
frequently these ants were engaged in taking nectar and in biting 
into tender twigs and the tiny fruit before the petals had fallen 

Bumblebees worked in the orchards during periods far too 
cold for the honeybee. Andrenids and other small bees were very 
sensitive to wind movement; they hung to leeward, and as a breeze 
increased to a gentle wind they disapoeared. Honeybees were only 
slightly affected by a breeze of sufficient velocity to stop the 
andrenids . Wild bees were more in evidence near uncultivated lands . 
Blowflies were extremely active on pear blossoms, particularly for 
several hours before a rain. They also appeared on the sunny sides 
of tree trunks and limbs, and fed freely upon the fluid oozing from 
blight infections, where no honeybees were found. Syrphid flies 
evidently fed more or less on the pollen, but the chief interest of 
flies in general was in nectar. 

. . . Note the abundance of the honeybee as compared with the 
other insects. 

- 6 - 

TABLE 2. — Comparison of insect visitors observed on apple, cherry, 
pear, and plum blossoms at Camino, Calif., during the 
seasons of 1932 and 1933 




Number i 
of. insects 

Percent of 
total visitors 





926 : 

33 J 



! 5.8 

Syrphid flies ..... 


: 1.5 


: 1.3 







: 100.0 


Increased Areas under Cultivation 

Cultivation of the land destroys the nest3 of beneficial insects 
and discourages rehabitation. The 1940 census reports a decrease in farm 
wood lots (nesting sites) of over 53 million acres since 1910. 

Brittain, W. H. 

1933. Apple pollination studies in the Annapolis Valley, N. S., Canada, 
1928-1932. Canada Dept. Agr. Bui. 162, 198 pp. 

p. 92: Observations were made by Hooper (1929 and 1931) over 
several years on the numbers of various insects visiting apple blossoms, 
and the numbers added up. The district contained many cherry, apple 
and other fruit plantations and numbers of hive bees were kept. The 
land not in orchard was either ploughed land or sheep pasture, not 
very suitable for pollinating insects. The counts on apple were as 
follows : 

Hive bees 374 

Bumble bees 37 

Halicti, etc 21 

Flies 23 

Beetles 104 

Ants 51 

Earwigs •• 3 

Thrips 2 

p. 93 J Bumble bees are a variable quantity. They are numerous 
in the region of the North Mountain, and especially in certain seasons, 
as in 1930, were a decided factor in pollination of an orchard at 
Blomidon, but in 1931 were much less numerous. In 1932 there was an 
apparent increase at some points, but, taking the area as a whole, they 

- 9 - 

cannot be considered an important factor in apple pollination. There 
is considerable testimony to the effect that the bumble bee population 
has declined in recent years . Formerly, it is said that they were 
common in more or less damp meadows where hand mowing had to be re- 
sorted to, but are now much less frequently found, especially in the 
Valley proper . Whether this is actually the case, and whether, if 
true, it is due to limitation of breeding places, poisoning, or some 
other factor, cannot now be determined. 

p. 96: Without pursuing this subject further, it may be 
pointed out that roadside banks,, pastures and dykes do not represent 
exactly wild conditions, but are the product of human activity. How- 
ever, neither are such locations intensively cultivated. Cultivated 
land and certain soil types, such as light sand or gravel, are not 
suited to nesting , which is one reason that the solitary bees are more 
numerous in such places as Long Island and along the North Mountain, 
than they are at many points situated in the middle of the Valley . 

p. 108: In 1932 the number was less, corresponding to an ap- 
parent decrease in the solitary bee fauna from all stations . This ob- 
servation may be correlated with a heavy mortality occurring among 
the solitary bees in the summer of 1931, apparently due to drowning in 
the nests following wet weather . 

Huts on, R. 

1926. Relation of the honeybee to fruit pollination in New Jersey. 
N. J. Agr. Expt. Sta. Bui. 434, 32 pp. 

pp. 10-12: The difference in the number of insects present 
in the cultivated Triangle plot . . . practically surrounded by tilled 
land, and in the cultivated Starr planting situated beside overgrown 
land is quite marked. 

Family Triangle Starr 

Chironomidae — midges 

Bombidae — bumblebees 

Syrphidae — syrphus flies 

Scarabaeidae — beetles 

p. 27: It has been generally demonstrated that insects, es- 
pecially honeybees, are factors in the set of fruit. 

Another factor is the comparatively high state of cultivation 
obtaining in the orcharding districts, which destroys hibernating 
places. The conditions do not obtain in the cranberry bogs which are 
surrounded by overgrown land, as cranberries do not bloom until July, 
giving ample time for breeding. 









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p. 29: The number of species of insects acting as fruit pol- 
lenators in southern Ven Jersey is small; the number of individuals 
other than honeybees is small, the lack of pollenizers being most 
serious in apple and pear orchards situated in cultured areas, less 
serious adjacent to uncultivated land, and not a problem at all on 
cranberry bogs, surrounded, as they are, with woodland, and blooming 
two months later than apple and pear. 

Honeybees and bumblebees are the most important insect polleni- 
zers in southern New Jersey, The ease with which honeybees can be 
supplied as needed is the deciding factor in making them the most 
dependable pollenizers. 

Johnston, S. 

1927. Pollination, an important factor in successful pear production. 

Mich. State Hort. Soc. Ann. Rpt. 1927: 196-199. 

p. 199: Bees or other suitable insects are therefore 
necessary for pollen transfer. While other insects carry pollen to 
some extent, the honeybee has no equal in this respect. Unfortunately, 
tame bees have been greatly reduced in numbers throughout the State 
by foulbrood, a very serious disease of bees, while the wild bees have 
been greatly reduced in numbers through the extermination of our forests 
and the thoughtless cutting and robbing of bee trees . 

Legasse, F. S. 

1928. Proper pollination of fruit blossoms. Del. Univ. Agr. Ext. Bui. 

15, 20 pp. 

p. 5: Poor sets of fruit have long been associated with 
rainy weather during the blossoming season. We have learned that this 
is due to the fact that honey bees, particularly the domesticated ones, 
do not fly extensively during rainy, cool, and windy weather, rather 
than to the effect of the rain on the blossoms themselves. This is 
another condition over which we have little control. The only possible 
remedy lies in the harboring of greater numbers of certain wild in- 
sects, such as the wild honey bee, which fly under weather conditions 
that cause the domesticated bee to cling closely to the hive. However . 
the prevalent system of clean cultivation and cover crops, furnishes 
no nesting place for the wild bees and is not conducive to their mul- 
tiplication in our orchards . 

Murneek, A. E. 

1930. Fruit pollination. Mo. Agr. Expt. St a. Bui. 283, U. pp. 

p.l: Almost all fruit grown in Missouri are pollinated by 
insects. Wind is no factor in fruit pollination. When the orchard 
is small and there is a great deal of waste land in close proximity, 
enough wild bees, bumble bees and other insects may be present in the 
spring to be of benefit in pollination. But in a region where most of 

-.11 - 

the land is under cultivation, the common honeybee is the only 
insect to reply upon . They are the only pollenizer under the 
control of man. 

Murneek, A. E. 

1937. Pollination and fruit setting. Mo. Agr. Expt. Sta. Bui. 379, 
28 pp. 

p. 13 j Of the various kinds of insects that visit flowers 
early in the spring, the common honeybee is by far in the majority. 
Moreover, it has been demonstrated in a convincing way that bees 
are of great value in pollination of apples, pears, cherries, plums 
and many other fruits. This is particularly true in sections where 
most of the ground has been put under cultivation with very little 
waste land left to harbor wild insects . 

Phillips, E. F. 

1933* Insects collected on apple blossoms in western New York. Jour. 
Agr. Res. 46: 851-862. 

p. 861: It seems probable that the scarcity of wild insects 
on apple blossoms is due to a combination of factors incident to the 
agriculture of the fruit districts. The relatively high land values 
tend to reduce waste land and wood lots and also tend to eliminate 
the wide fence rows which are favored nesting places for some species . 
Cultivation reduces nesting and hibernating places, especially of 
solitary bees. Clean cultivation of orchards f where practiced, still 
further reduces the opportunities for the propagation of wild bees . 
It is possible that the efforts of fruit growers to control injurious 
insects in some degree serves to destroy individuals of those species 
which are beneficial. Beekeepers have observed that dusting destroys 
many honeybees, and it is probably equally disastrous to solitary bees. 

Tysdal, H. V. 

1940. Is tripping necessary for seed setting in alfalfa? Amer. Soc. 
Agron. Jour. 32: 570-585. 

p. 583: The most effective pollinators in this study have 
been Megachile and Nonda bees, several species of which have been 
observed working on alfalfa. Other conditions being favorable, it 
would appear that one of the most effective means of insuring a seed 
crop of alfalfa would be a supply of these small, relatively harmless, 
hard-working insects. It should, therefore, be sound agronomic prac- 
tice to encourage their presence in an alfalfa seed field. The writer 
has talked with alfalfa seed growers who have plowed through a large 
colony of these bees, which often make their home in the ground, and 
in some instances it has been known that such practices have destroyed 
the entire colony ^ or at least caused it to move. 

p. 584: Entomologists who have observed the alfalfa pollinating 
insect population in Nebraska for many years unhesitatingly state 

- 12 - 

that there are fewer colonies of Noroia species and fewer of 
Megachile species than formerly. It is possible that cultivation 
and settlement has disturbed the wild bees and thus reduced their 
number. Hence, it is suggested that a decrease in the population 
of these beneficial insects, together with a possible increase in 
harmful insects, may be an explanation for the uncertainty in 
alfalfa seed production in formerly good seed-producing areas. 

Concentrated Plantings 

Wild pollinating insects apparently do not range widely for food, and 
since they do not store an appreciable amount of food, concentrated plant- 
ings of one crop are not favorable for their development. 

Brittain, W. H. 

1933. Apple pollination studies in the Annapolis Valley, N. S., 
Canada, 1928-1932. Canada Dept. Agr. Bui. 162, 198 pp. 

p. 9: It should be emphasized, however, that a few colonies 
of bees placed in an orchard surrounded by large acreages devoid of 
bees is of little or no value . In such situations it may be neces- 
sary to have a concentration of from 35 to 50 colonies in order to 
ensure the pollination of the particular orchard in which the bees 
are placed . In districts where beekeeping is general, however, and 
neighbouring orchards are similarly supplied, one colony to the 
acre or even one colony to four acres may be sufficient. Cwing to 
the many factors involved more exact figures cannot be given. It 
must suffice to point out that the provision of as many colonies as 
practicable is a useful measure of insurance against unfavourable 
weather, and a scarcity of wild pollinators, since it is only the 
hive bees that can be increased in numbers at will and placed where 
needed in the orchards. Unfortunately, at the present time, there 
is no adequate local supply; inexperience in beekeeping and the 
danger of poisoning prevents many from adopting this practice who 
would otherwise do so . 

Hootman, D. H. 

1930. The importance of pollination and the honey-bee in fruit yields. 
N.Y. State Hort. Soc. Proc. 1930 t 49-58. 

The location and size of the individual orchard are apparently 
the factors that determine whether or not bees are needed. Orchards 
not too large in size with varieties well mixed, located near woods, 
swamps or uncultivated land where wild insects can winter over in 
large numbers, usually set a satisfactory crop without additional 
bees . With the conditions that exist in commercial fruit sections 
where whole communities are engaged in fruit growing and where 
orchards have been planted by the square mile the wild insects are wholly 
inadequate to pollinate effectively the vast expanse of bloom . It is 

- 13 - 

in these locations especially that commercial fruit growers are 
largely dependent upon the honeybee — the only insect admirably 
adapted for pollinating fruit bloom that can be readily controlled 
by man. 

Kearney, T. H. 

1923. Self-fertilization and cross-fertilization in Pima cotton. U. S. 
Dept. Agr. Dept. Bui. 1134, 68 pp. 

p. 49x Observation in Arizona has shown that the number of 
efficient pollinating insects differs greatly in different localities . 2/ 
Bees and other active pollinators are normally abundant amon? the 
cotton flowers at Sacaton throughout the summer, and -the entire 
surface of the stigmas is almost invariably well covered with pollen 
soon after the corolla has opened. On the other hand, observations 
in the Salt River Valley, at distances of 25 to 4-0 miles from Sacaton, 
have shown that insect pollination of cotton there is often much less 
rapid and complete. The probable explanation is that in recent years 
an extensive and almost continuous acreage has been planted to cotton, 
and the insect population is not large enough to insure thorough 
pollination of all the flowers. 

Thus, on July 18, 1919, in a field situated near Tempe in the 
heart of the cotton-growing district, no pollen grains were observed 
upon the extrastaminal portion of the stigmas at 9 a.m. and very few 
at 10 a.m. late in the afternoon of July 20, 1920, inspection of the 
same field showed the extrastaminal portion of the stigmas to be 
free from pollen in most of the flowers, while the remaining bore only 
a few insect-transported grains. None of the flowers examined showed 
thorough pollination of the whole stigma tic surface. Two other cen- 
trally located fields, one at Phoenix and one near Tempe, which were 
examined at 5 p.m. on August 5 and at 4- p.m. on August 6, showed simi- 
larly deficient pollination. On the other hand, in fields situated 
on the outskirts of the valley, at Iitchfield and at Goodyear, which 
were examined at noon on the same days, bee3 and other pollinators 
were abundant, and the stigmas of the cotton flowers were found to be 
well covered with pollen. 

p. 50 : In the mean number of seeds per 100 flowers, a value 
which integrates the percentage of bolls matured and the mean number 
of^ seeds per boll, the increase due to artificial pollination amounted 
to* 32 per cent, indicating that a substantially greater crop both of 
seed and of fiber might be expected if bees were abundant in the Salt 
River Valley cotton fields during the blossoming period . 

2/ A pronounced difference in the abundance of pollinating insects at 
different localities in Arizona was noted by Cook, McLachlan, and Meade. n At 
the time of our visits to the fields at Yuma and Sacaton there was a notable 
difference in the activity of the insects at the two places. Several species 
of large wild bees that were industriously visiting the flowers at Yuma in 
September were not seen at all at Sacaton." 

- 14 - 

Luce, W. A., and Morris, 0. M. 

1928. Pollination of deciduous fruits. Wash. Agr. Expt. Sta. Bui. 
223, 22 pp. 

p. 21: Observations made at Wenatchee in the spring of 
1926 and 1927 developed the fact that there are relatively few insects 
visiting the apple blossom in many orchards. These examinations showed 
that there was a lack of insect activity necessary to perform the cross- 
pollinizing in commercial orchards. In orchards where there were still 
plenty of trees of several different varieties the failure of a crop 
was apparently due to lack of insect activity at blossom time. Orchards 
nearest the foot hills or open country produced the heaviest set of 
fruit. The native bees and insects came in abundance from the rocky or 
hilly ground near these o rchards. This condition has been known to 
prevail in many local districts for several different years . 

Where wild bees and other insects are abundant, a minimum 
amount of help is needed from the honey bee, but in the large closely 
planted commercial sections, where there are very few wild bees and 
other insects visiti ng the blos soms, more honey bees should be pro- 
vided . 

Rail-Fence Elimination and Heavy Grazing 

Rail fences constitute ideal nesting places for many species of 
pollinating insects. The replacement of rail by wire fences has destroyed 
such nesting places, for wire fences permit clean, close cultivation. The 
increase in the output of wire fences and their relative cheapness has 
facilitated the use of stock for cleaning up fence rows and out-of-the way 
patches of land which would otherwise harbor pollinating insects. 

It is an axiom in beekeeping that bees starve on sheep ranges. The 
sheep trample the ground and eat the vegetation into the ground, leaving 
few flowering plants. 

There has been an increase of more than 4. million head of sheep on 
farms since 1910. 

The practice of pasturing sheep in woodlands is detrimental to the 
propagation of wild pollinating insects. 

Sims, I. H., Munns, E. N., and Auten, J. T. 

1938. Management of forest soils. TJ. S. Dept. Agr. Yearbook (Soils 
and Men) 1938: 737-750. 

p. 74-4: The number of livestock grazing the farm woods in the 
Central States is estimated to be five times the actual carrying 
capacity and is maintained largely by supplementary feeding of crop 

- 15 - 

Spencer, D. A., and Potts, CO. 

1933. Sheep raising in U. S. has changed greatly since pioneer period. 
U. S. Dept. Agr. Yearbook 1933: 264-273. 

p. 264: Sheep are also raised extensively in the grass-produc- 
ing areas of the Eastern and Central States, particularly in rolling 
and hilly sections . Since sheep are fond of a great variety of weeds 
and underbrush which cattle and horses do not relish, they are useful 
in keeping fields and fence .corners clean and in utilizing forage 
not so well adapted to other livestock. 

p. 267: Except where flocks are kept to produce purebred stock, 
special crops are seldom grown for the sheep, which -are generally 
turned onto pasture as soon as the grass begins to grow in the soring 
and remain there until the crop s have been harvested, when they are 
usually given the run of the fields to graze and to clean up the 
weeds , and remain there until snow falls. They are then carried 
through the winter on hay and some of the unsalable roughage, with 
little or no grain. 

Forest. Brush, and Grass Fires 

Forest, brush, and grass fires destroy all kinds of wild life, includ- 
ing pollinating insects. The practice of burning fence rows, railroad 
right-of-ways, pastures, etc., is highly detrimental to wild pollinating 
insects, most of which nest in or near the ground. 

Sims, I. H., Munns, E. N., and Auten, J. T. 

1938. Management of forest soils. U. S. Dept. Agr. Yearbook (Soils 
and Men) 1938 t 737-750. 

p. 741 1 Heavy cutting has commonly been followed by fire, and 
examples of serious soil deterioration due to this combination of 
treatments can be found in practically every forest region of the 
country. Some 60 million acres of land have been so completely dev- 
astated by this combination that they are unlikely to reforest 
naturally and must be planted. The total is being swelled currently 
by the addition of 850,000 acres each year, three-fourths of which 
is land formerly occupied by conifer stands. 

When cut-over land is burned the fire accomplishes in minutes 
the degree of litter removal that would be achieved naturally only 
after several years... This sudden removal of the litter and its 
living population sets in motion a chain of events leading directly 
to deterioration or loss of the soil. 

p. 743: Extreme soil temperatures frequently develop during 
the great conflagrations and humus in the upper horizons is oxidized 

- 16 - 

immediately. The mineral soil has much the same appearance as 
samples ignited in a furnace. Accumulations of heavy debris burn 
• with such intensity that the soil is sterilized for years . 

The Automobile and Paved Roads 

Fast-traveling automobiles kill large numbers of pollinating insects. 
For every slow, awkward female bumblebee killed in the spring there is 
one less nest of pollinating insects later in the year. Improved, well- 
kept roads offer little refuge for wild pollinating insects. 

Pickles, W. 

194-2. Animal mortality on three miles of Yorkshire roads. Jour. Anim. 
Ecol. Ill 37-43. 

p. 38: As with the Coleoptera, the Hymenoptera, chiefly bees, 
have met their deaths either by being crushed by the wheels of the 
vehicles, or in the manner indicated above. 

p. 40 r A busy road passing through a country district has 
a big effect on the animal life in its vicinity. 

Throughout the year 1938, the total number of animals (insects) 
killed on the 3 miles of road under observation was 6P7... This is 
229 per mile; of which 113.3 were Hymenoptera. 

pp. 41-42: Altogether, there were 4-2 different species of 
animals killed on the roads. [The Hymenoptera included were as 
f 0II0W8 : ] 

Bombus terrestris L. Apis mellifera L. 

B. la pi da ri us L. Colletes succinata L. 

B. muscorum L . Andrena armata Gmel. 

B. agrbrum F. Vespula vulgaris L. 

B. ruderatus F. V. germanica F. 

Poisoning from Insecticides 

Thousands of colonies of honeybees are killed each year by arsenical 
sprays and dusts. Often the losses occur long after the insecticides have 
been applied, when brood is fed stored poisoned pollen. Under such condi- 
tions bees gradually dwindle and die, and often the owner is not aware of 
the true cause. 

At one time, poisoning of honeybees was confined largely to the fruit- 
blossoming period, when bees took poison from open blossoms, but now the 
poisoning continues throughout most the summer because many cover sprays 
are applied to control injurious insects, particularly the codling moth. 
Sprays and dusts falling on cover crops in orchards kill both honeybees 

- 17 - 

and native s. The dusting of cotton, potatoes 4 and vegetables takes 
a heavy annua] toll of bees. 

From the knowledge of the habits of wili poll i i ects and 
the fact that the queens obtain their food directly from flowers, they 
would appear to be even more susceptible to insecticides than honeybees, 
since the queen's food is not nectar and pollen but royal Jelly. Brittain 
made observations on this point, but came to no definite conclusions as 
to the over-all effect of the use of insecticides on wild pollinating 
insects. He did find, however, lethal amounts of arsenic in pollen in 
the nests of wild bees. 


On the following pages will be found a few selected references to 
the value of the honeybee in pollinating crops, as mentioned in articles 
by recognized authorities in horticulture and agronomy. 

ELetz, K. F. 

1925. Pollination and the honey bee. Ind. Conserv. Comn. Pub. 52, 
20 pp. 

pp. 19-20: One thing is certain. The honeyb ee represents 
the hi ghe st point that has been re ached in the. insec t world as a 
flower polli n ato r^ _Its_ ow n ex iste nce in both t he larval and 
adult stage are dependent on either pollen or nectar. The ha bits 
that it possess es of wo rking one kind of flower at a time make it 
a more effective pollinator than an insect that visits al l flowers 
promiscuously . . . 

And finally the honeybee is the only one of the insect pollinators 
that man has under his control or domesticated, so to speak. All 
the rest are subject to all the vicissitudes of nature, including 
unfavorable weather conditions, food shortage, which cannot be 
supplied, and the inroads of natural enemies, including Man. Man 
through h is varied, often thoughtless and multitudinous activities , 
is the greatest disturber of the natu ral order of things , and w hat 
he does he must pay the price for in one manner or another . How- 
ever , by studying the ways of nature he often corrects his errors 
and when he needs a general flow e r polli na tor he has bu t to try 
the honey bee. 

Vansell, G. P., and deOng, E. R. 

1925. A survey of beekeeping in California and the honeybee as pollini- 
zer. Calif. Agr. Expt. Sta. Cir. 297, 22 pp. 


pp. 17-18: Of all the insects that visit flowers, bees are 
the b est adapted by the st ruc ture of the body to act as c arri ers of 
pollen . The body and legs are covered with heavy, stiff hairs which 
are branched or feather like. These catch and hold the p ollen grains , 
until they are brushed into a "pollen basket" on the hind leg. In 

- 18 - 

this carrier the load of pollen is transported to the hive. 
However, all bees are not of equal value as pollinizers as some 
of them do not visit all types of flowers. The honeybee and the 
bumblebee, however, visit almost all flowers with little restriction 
except that they evidently confine themselves to a single species 
on any one trip. 

We have many native species of bees such as bumblebees, car- 
penter bee, leaf cutters and others, but only in rare instances are 
any of these active during the early spring and then only in very 
restricted numbers. 

The bumblebee is one of the earliest of the native bees to 
feed in the spring, but the entire colony, except the queen, nerishes 
during the winter. 

In the spring the whole responsibility of rebuilding the 
colony devolves upon the queen. She lays and incubates the eggs, 
seven to sixteen in number , feeds the newly hatched larvae and only 
after the first brood matures can she give her strength entirely to 
brood rearing. By fall the colony may have grown to a size of 
from one to five hundred individuals. Certain of the mining bees, 
Halictus. which nest in certain cliffs, have one or two generations 
a year. The spring generation consists of hibernating, fertilized 
females which give rise to a summer generation. The leaf-cutting 
bee, Megachile spp., apparently has but one generation a year and 
includes but a small number of individuals . The carpenter-bee, 
Ceratina dupla, has two broods a year which are very restricted in 
numbers • 

These examples are typical of the life history of our common 
native species of bees that have from one to five or six brood cycles 
annually, while the number of individuals range from a score to a few 
hundred . Comparing this with the honeybee's record of from twelve to 
fifteen brood cycles a year, all the descendants of a single queen . 
which may reach a hundred thousand bees annually, or more, we realize 
the wonderful reproductive powers of this insect. It should also be 
noted that instead of the death of all the workers, the winter's mor- 
tality among honey bees is usually very slight. From five hundred to 
sixty thousand may be present in a single colony at the close of winter 
and two or more brood cycles may be reared in the spring before many 
of the fruit trees bloom. 

Fruit Crops 

Gould, H. P. 

1939. Why fruit trees fail to bear. U. S. Cept. Agr. Leaflet 172, 
5 PP. 

pp. 3-4: Self -sterility is very common. It occurs in many 
varieties of apples , most varieties of pears, probably in all varieties 
of sweet cherries , in most if not all varieties of the native and 

- 19 - 

Japanese plums, and in some varieties of European or d omesti c plums 
and prunes . Sour cherries are considered largely self -fertile, al- 
though there is some evidence of partial self-sterility. Kost peach 
varieties are self -fertile; the J. H. Hale and June Elbert a (Mikado) 
are notable exceptions, as they require cross- pol lination . Sterility 
in plums, cherries, and perhaps other fruits may sometimes be due to 
deformed or imperfect pistils. Some grape varieties must be cross- 
pollinated in order to be fruitful. 

There is every conceivable degree of self-sterility, from one 
extreme where no fruit sets without cross-pollination to that where 
it is so slight as not to be a serious factor in fruit production. 
The opinion is commonly held that even the varieties considered to 
be self-fertile in a high degree will set a better crop of fruit if 
cross-pollination occurs . With self-sterility prevailing to so large 
an extent in common fruit varieties, the relation of weather condition s 
favorable to the greatest activity of honeybees becomes readily appar- 
ent, since it is on them that the fruit grower must depend very large - 
ly for the cross-pollination of his fruits . 

When self-sterile varieties are planted and there are no other 
trees of different varieties of the same kind growing near enough to 
insure the passing of bees from one to the other, it will be found 
that trees blossom but do not set fruit . 

When the tree to be cross-pollinated is in bloom secure some 
blossoming branches from a tree of another variety of the same kind 
of fruit and place them in a pail or other water container in the top 
of the tree. The bees, visiting the trees, will also visit the blossoms 
on the branches and will thereby transfer the pollen as they revisit 
the blossoms on the tree . 

Mumeek, A. E. 

1930. Fruit pollination. Mo. Agr. Expt. Sta. Bui. 283, 12 pp. 

p. It With proper care bees winter over in large numbers and 
are very active in the spring. They are especially well adapted to 
carry pollen. Their bodies and legs are covered with hairs to which 
the pollen grains adhere in large numbers. Moreover, the h o neybee 
visits only one kind of flower, like the apple or the peach , at a 
time . Thus they are very effective agents in cross-pollination . 

p. 9: It has been demonstrated in many orchards in a convincing 
way that bees are of great value for the pollination of apples . 
sour cherries, and other fruits . If the orchardist does not keep his 
own bees and there are none in the neighborhood, then most certainly 
it will pay to secure several hives. 


- 20 - 

Philp, G. L., and Vansell, 0. H. 

1932. Pollination of deciduous fruits by bees. Calif. A«rr. Col. *bct. 
Cir. 62, 27 pp. 

p. 4.: The fruit grower has a pollination problem with almonds , 
cherries, plums and prunes, apples, pears , and berries. In general, 
apricots, peaches , and walnuts set well with their own pollen and 
hence present no difficulties from this standpoint. The J. H. Hale 
peach, however, is self-unfruitful and must be interplanted with 
some other variety. Recent studies indicate that some varieties of 
walnuts in certain years do not mature the standnate and pistillate 
flowers at the same time and therefore, under these conditions, can- 
not pollinate themselves. 

p. 5: Bees are the most important insects for this work. The 
grower should therefore have plenty of bees in the orchard during 
the blossoming period. 

[Honeybees are rented for the pollination of almonds, apples, avo- 
cados, cranberries, pears, plums, prunes and cherries, as well as cucumbers 
and alsike clover. 1 


Tufts, W. P., and Philp, Guy L. 

1922. Almond pollination. Calif. Agr. Expt. Sta. Bui. 34-6, 35 pp. 

p. 24.: Pollenizing agencies, such as the honey bee, are neces- 
sary to the set of a good crop of fruit. One colony of honey bees 
should be provided for each acre of orchard. 

Crane, H. L., and Reed, C. A. 

1937. Nut breeding. U. S. Dept. Agr. Yearbook 1937: 827-889. 

p. 872 j The pollen of almond and tung trees is carried by 


Auchter, E. C. 

1924. The importance of proper pollination in fruit yields. N. J. State 
Hort. Soc. Proc. 1924: 133-K2. 

pp. I4.O-I4.I1 The value of bees in pollination. The carrying of 
pollen from one variety to another is accomplished by wind and bees. 
It has been found, however, that pollen is carried only very short 
distances by wind, but that bees play a very important part in carrying 
the pollen. 

In crossing into the blossoms to ?et the nectar, their bodies 
become dusted with the pollen. This pollen is then left on the stigmas 
of other blossoms when they are visited. In California the invest!- 

- 21 - 

gators are recommending one hive of bees per acre for pollination 
purposes . 

A few years ago, the writer helped to conduct a special test 
to prove the value of cross-pollination and bees in a bearing Rome 
Beauty orchard in West Virginia. This orchard consisted of approxi- 
mately twenty acres and was planted at quite a distance from any 
other orchards. Although it blossomed well each year, the set was 
always very light. During the blossoming time for two years bees 
were placed under sixteen trees in the center of the orchard and 
blossoming limbs of other varieties were secured and placed in 
pails of water, which were hung in the Rome Beauty trees. The b ees 
worked back and forth through these blossoms and an excellent set 
was secured each year on the se si xteen trees . T he rest of the 
orchard, at some distance from the bees, set only a light crop . 

A similar test conducted in 1922 in a bearing Stayman Winesap 
orchard in Maryland where bees were placed in the orchard, together 
with blossoming branches of the York Imperial variety in nails of 
water, resulted in a fair crop of fruit being set, even thoug h the 
season was unfavorable for pollination purposes due to some frosts 
and cold windy weather * In previous years, without bees or the 
York Imperial blossoms, very little fruit "set" although there were 
plenty of Stayman blossoms and the weather was favorable . 

In 1923 with good pollination weather and Grimes blossoms placed 
about the bee hives, a good set of fruit was obtained in this orchard. 

In some special tests at the Experiment Station in 1923, two 
trees, one a Grimes and one a Stayman Winesap, 40 feet apart, were 
inclosed in a large muslin frame 1A. feet wide, 14 feet high, and 55 
feet long. 

A muslin partition was built through the center of the tent 
(long ways) so that one-half of each tree was on one side of the 
partition and one-half of each tree was on the other side. Bees 
were placed in one side of the tent, so that they could fly back and 
forth between the halves of the Grimes and Stayman Winesap trees. 
No bees were placed in the other side of the tent. In the side in 
which bees were placed, fruit set on the halves of both the Stayman 
Winesap and Grimes trees . In the other side of the tent without bees , 
no fruit set on the halves of the same Stayman Winesap tree, although 
the Grimes, being a self -fertile variety, did set some fruit . Appar- 
ently in the one-half of the tent, the Grimes pollen was carried b y_ 
the bees to the Stayman Winesap, giving a set, while in the other 
half, the Grimes pollen did not reach the Stayman blossoms. 

- 22 - 

Another test of the value of bees was indicated in some experi- 
ments carried on at the College in 1923. Two hundred and fifty- 
blossoms each of Baldwin, Lawyer, Stayman Winesao and Kinnaird were 
emasculated and left unbagged or open to cross-pollination. Appar- 
ently, because all of the petals had been removed by emasculation, 
the bees were not attracted to these blossoms. As a result, not a 
blossom on any of the emasculated blooms "set." Other unemasculated 
blossoms (with their petals expanded) on the same limbs were appar- 
ently visited by the bees so that cross-pollination took place. In 
these cases 21.4. per cent of the Lawyer blossoms, 6.4 per cent of the 
Kinnaird, 15.8 per cent of the Baldwin, and 5.3 per cent of the 
Stayman Winesap "set" fruit. 

From the above experiments, it can be seen how important it is 
for orchardists to have several hives of bees scattered through their 
orchards. The last experiment also suggests that a great many bees 
might be killed if poisonous sprays are used when the petals of the 
blossoms are showing . 

MacDaniels, L. H., and Heinicke, A. J. 

1929. Pollination and other factors affecting the set of fruit, with 
special reference to the apple. N. T. (Cornell) Agr. Expt. 
Sta. Bui. 497, 47 pp. 

pp. 4.-5* The flowers of the apple and of most of our fruit 
plants are adapted by their structure to insect pollination. The 
showy petals, the odor, and the nectar-secreting glands have the 
function of attracting insects which carry the pollen from flower 
to flower. The pollen itself is of the sticky tyoe that adheres 
to the hairy coat of insects which visit the blossoms ... rather 
than of the light dry type that is adapted to wind dissemination. 
When it is appreciated that it would take approximately 4.00 apple- 
pollen grains placed side by side to reach from one end of a bee to 
the other, and that the number carried by a single bee might easily 
approximate 100.000. some idea of the possible effectiveness of 
insect pollination can be gained. 

Overholser, E. L. 

1927. Apple pollination studies in California. Calif. Agr. Expt. 
Bui. 426, 17 pp. 

p. 15: The use of bees as a means of effecting pollination 
in an apple orchard greatly increased +he set of fruit when con- 
trasted with the normal set. 

Cross-pollination increased the set of fruit, even with self- 
fruitful varieties like the Yellow Newtown. 

Swinson, C. R., Weaver, F. P., Dadisman, A. J., Vernon, J. J., Gould, H. P., 
and Lincer, J. B. 

- 23 - 

1927. Factors influencing the yield of apples in the Cumberland- 
Shenandoah region of Pennsylvania, Virginia, West Virginia. 
U. S. Dept. Agr. Tech. Bui. 54, 25 po. 

p. 21: A number of growers attributed low yields to failure 
of fruit to set. It was commonly observed that the low yields of 
the Winesap and varieties of the Winesap family were ascribed to 
this factor. These varieties are largely self-sterile and must be 
cross-pollinated by some other variety. Self-sterile varieties 
should not be planted in solid blocks or isolated from other orchards. 
Where self-sterile varieties have been so planted the results may be 
improved by top-working every fourth or fifth tree in every fourth 
or fifth row with some variety that is a good cross-pollinizer. Bees 
are essential in any orchard and are effective in securing pollina- 
tion even during cold, wet seasons . 


Stout, A. B. 

1933. The pollination of avocados. Fla. Agr. Expt. Sta. Bui. 257, 
44 pp. 

p. 42: It is without doubt advisable (1) to interplant 
avocados on the basis of their flower behavior (2) to supply bees 
in abundance to effect pollination . 

Traub, H. P., Pomeroy, C. 3., Robinson, T. R., and Aldrich, W. W. 

1941. Avocado production in the United States. U. S. Dept. Agr. Cir. 
620, 20 pp. 

p. 3: With some varieties, as Fuerte, there is sufficient 
overlap of the two sets of flowers to render them self-fertile; with 
other varieties, a sufficient percentage of single-cycle flowers 
(completing their anthesis in one opening) are produced to render 
self-pollination easy of accomplishment, the only requirement in 
each case being the activity of bees or other insects ... . 

Keeping bees in or about the orchard is also considered a 
wise provision during the blooming period. Observations indicate 
that pollen is carried considerable distances by bees and doubtless 
by other flying insects. 


Darrow, G, M. 

1937. Blackberry and raspberry improvement. U. S. Dept. Agr. Year- 
book 1937: 496-533. 

p. 498: Normally the wild blackberries of the East are entirely 

- 24 - 

or nearly self-sterile, and those of the Pacific coast have male 
and female organs on separate plants. All need cross-pollination . 
In the clearings and pastures bees and other insects have crossed 
the blackberry species for the last 100 to 300 years . 

Raspberry, Blackberry, Dewberry f Rubus ) 

Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 608 pp. Philadelphia. 

p. 340: Pollination. As a rule the anthers and stigmas mature 
simultaneously. There is abundant nectar secreted by a fleshy ring 
on the margin of the receptacle, inside of the stamens. Insects 
facilitate pollination. Better yields are secured, in the case of 
some dewberries, if they are planted adjacent to another variety so 
that cross-fertilization will result. 

Blueberry and Huckleberry 

Merrill, T. A. 

1936. Pollination of the liighbush blueberry. Mich. Agr. Expt. Sta. 
Tech. Bui. 151, 34 pp. 

p. 33: Of much greater importance than self or cross-pollina- 
tion, though it receives little space in this report, is the need 
of insuring some (any) sort of pollination. Mechanical aid is 
absolutely necessary to a good set, from self as well as from cross- 

Bumble-bees and honey bees play a very active part in blueberry 
pollination . 

Phipps, C. R. 

1930. Blueberry and huckleberry insects. Maine Agr. Expt. Sta. Bui. 
356, pp. 107-232. 

p. 116: In conclusion, then, the investigations thus far have 
shown: (1) that various species of insects, especially honey-bees . 
bumble-bees and other bees, collect blueberry pollen; (2) that such 
insects undoubtedly exert a marked influence on blueberry pollina- 
tion since their exclusion affects yields so strikingly. 


Lagasse, F. S. 

1928. Proper pollination of fruit blossoms. Del. Univ. Agr. Ext. 
Bui. 15, 20 pp. 

- 25 - 

p. 10: The exDerimental results obtained in different 
sections of the country on the sour cherry with respect to its 
self-fertility do not entirely agree. The majority of evidence, 
however, indicates that most varieties will set commercial crops 
thru the use of their own pollen. Shoemaker ... has recently 
shown that the set of Montmorency is increased under Ohio con- 
ditions by the use of early Richmond pollen, but it is doubtful 
whether the increased set will compensate for the space occupied 
by the trees of the inferior pollinating variety. Interplanting 
of several varieties, better cultural practices, and the place- 
ment of bees in the sour cherry orchard is recommended for in- 
creasing the set of fruit . 

Schuster, C. E. 

192$. Pollination and growing of the cherry. Oreg. Agr. Expt. Sta. 
Bui. 212, 4.0 pp. 

p. 23: With fruit so dependent upon cross-pollination as are 
cherries, the agents responsible for this transfer of pollen need 
to be considered. The number and presence of wild insects can be 
controlled very little, but the honey-bee can be controlled to a 
great extent. It is becoming the practice for cherry growers 
either to keep their own bees or to hire stands of bees during the 
blooming season. One hive to one or two acres of cherries is 
sufficient if the stands of bees are strong. 

The sour cherry may be self-sterile, self-fertile, or partly 
self-fertile, depending on the variety. 

Tufts, W. P., and Philp, G. L. 

1925. Pollination of the sweet cherry. Calif. Agr. Expt. Sta. Bui. 
385, 28 pp. 

p. 26: Pollinizing agencies, such as honey bees, are necessary 
to set a good fruit crop. 

At least one stand of bees should be provided for each acre 
of orchard. 


Darrow, G. M., Franklin, H. J., and Malde, 0. G. 

1924. Establishing cranberry fields. U. S. Dept. Agr. Farmers' Bui. 
U00, 37 pp. 

pp. 9-10: Results of investigations by the Massachusetts Agri- 
cultural Experiment Station indicate that in that State cranberry 
blossoms are pollinated by bees. Bumblebees and honey-bees seem to 
be the chief agents of pollination. As the former are not always 

- 26 - 

abundant many grow ers keep small _ api aries . 

Bees are not common in the cranberry region of Wisconsin, 
and experiments and observations by representatives of the Wisconsin 
Agricultural Experiment Station indicate that though they help in 
pollination they are not necessary in that State under normal con- 
ditions. The cranberry blossoms there seem to be practically self- 
fertile. After the flower bud opens ... the pistil grows past the 
anthers and may be fertilized then or later as the flower is jostled 
by the wind. Even in Wisconsin bees may be of great value in hasten- 
ing pollination, thus insuring un iformity in the time of setting and 
maturing the fruit. Without insect aid the pollina t ion is apt_ to 
extend over a long period and the fruit likel y to m ature unevenly . 


Beattie, W. R. 

1942. Cucumber growing. U. S. Dept. Agr. Farmers' Bui. 1563, 25 pp. 

pp. 12-13: Pollination , or the setting of fruit, on cucumber 
vines is dependent upon some outside agency such as bees . Two kinds 
of flowers are found on every fruiting cucumber plant — the male ones . 
which supply the pollen, and the female ones... which produce the 
cucumbers. They can be readily distinguished, as the female flower 
is borne on the outer end of the little cucumber. TTsually the male 
flowers appear in great abundance in advance of the female flowers, 
which leads to the erroneous notion that the cucumbers are failing 
to set fruit. Later, the female flowers appear, and fruit is formed. 
Cucumbers grown in the field are pollinated by either tame or wild 
bees from the neighborhood . Under favorable conditions, cucumbers 
grown in frames may be pollinated by natural agencies, but th e sash- 
cucumber growers of the Norfolk district provide hives of bees near 
their frames when the cucumbers are setting, in order to insure 
perfect pollination. Without proper pollination the cucumbers are 
deformed, or at least a considerable percentage of nubbins are pro- 
duced. In localities where bees are scarce it is advisable for the 
growers of cucumbers in fields to keep bees, in order to insure 
pollination . 


Hooper, C. H. 

1939. Hive bees in relation to commercial fruit production. Southeast. 
Agr. Col. Jour. 44: 103-108, illus. 

p. 106: There is an opinion that blossoms that have been 
pollinated resist frost better than those that have not been polli- 
nated ... In England a Cambridgeshire grower who had a large acreage 
of gooseberries and had hives of bees placed among them f in a year in 
which frost damaged his neighbours' crops, had a good crop which he 
attributed to his bees. 

- 27 - 

Gooseberry and Currant 

Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 608 pp. Philadelphia. 

p. 307 j Pollination. — Gooseberries and currants are cross- 
pollinated for the most part. Insects are the chief agents in 

Almeria Grape 

Olmo, H. P. 

1943. Pollination of the Almeria grape. Amer. Soc. Hort. Sci. 
Proc. 42: 401-406. 

p. 405: Einset (l) stated that no female grape varieties are 
grown commercially in this country because natural cross -pollination 
is inadequate to obtain good yields. The Almeria in California is 
an exception to this rule. This fact brings up the question as to 
whether grape breeders should continue to discard all female varieties 
without further tests of their qualities. The experience with the 
Almeria in California suggests that other female varieties, if they 
should possess particularly desirable qualities, might be grown 
commercially with profit if adequate cross-pollination is provided . 
Since it has been observed that bees do work on grape flowers, it 
appears that mere adequate cross-pollination may be provided for by 
introducing hives in commercial! plantings to supplement win d 
pollination . 

Fletcher, S. W. 

194-1. Pollination. Standard cyclopedia of horticulture, by L. H. 
Bailey, v. 3, pp. 2734-2737. New York 

p. 2736: Of one hundred and forty- five varieties of grapes 
tested by Beach, thirty-one were self-fertile, forty-one self- 
sterile, and seventy-three uncertain. 

Snyder, E. 

1937. Grape development and improvement. TJ. S. Dept. Agr. Yearbook 
1937: 631-664. 

pp. 639-40 : The blossoms of Vitis are arranged in a pyramidal, 
loosely branched cluster known as a panicle. In the wild state some 
vines may bear only male or standnate flowers, while others bear 
perfect or hermaphrodite flowers that have both stamens and pistils. 
American native species bear male flowers and hermaphrodite flowers 
on separate vines, while most European vines of Vitis vinifera bear 

— 28 — 

only hermaphrodite flowers . 

The hermaphrodite blossoms range from flowers having reflexed, 
very poorly developed stamens ... to perfect flowers with upright 
stamens ... Varieties with reflexed stamens usually do not set fruit, 
or set only very loose clusters, unless they are cross-pollinated, 
either naturally or artificially. 

The pollen grains are deposited on the stigma through natural 
or artificial means. 

Dearing, C. 

1935. Muscadine grapes. U. S. Dept. Agr. Farmers' Bui. 17P5, 36 pp. 

p. 17: The pollen is carried from the male to the pistillate 
flowers almost entirely by insects. 

While the honeybee is a less-effective pollinating insect for 
muscadine than for fruits with sticky pollen, such as apples, it 
appears to have sufficient value to warrant placing stands of bees 
in large vineyards during the blossoming season . 


Popenoe, W. 

1917. The pollination of the mango. U. S. Dept. Agr. Bui. 542, 20 pp. 

p. 4: In spite of the close proximity of anther and stigma, the 
transfer of pollen from the former to the latter does not seem to be 
accomplished easily. Both the stamen and the pistil retain an erect 
position throughout, and the pollen as it is shed usually falls upon 
the base of the ovary or upon the disk rather than upon the stigma. 

The normal method of transferring the pollen from the anther to 
the stigma must be through the agency of insects. 

p. 6: The industry with which the honeybee goes from flower to 
flower, systematically working over the surface of the disk with its 
proboscis to obtain all the nectar present, at the same time turning 
its body around in a circle and almost of necessity coming in contact 
with the anther in its circuit of the disk, makes this insect one of 
the most effective pollinating agents. 


Beattie, W. R. 

1926. Muskmelons. U. S. Dept. Agr. Farmers' Bui. 1£6£, 38 PP. 

p. 21: Growers frequently inquire why the early blossoms on 
their muskmelons do not set fruit. Muskmelon blossoms are of two 
kinds, staminate and pistillate, or male and female. Following the 

- 29 - 

natural tendency of all vine crops, a large number of male blossoms 
appear in advance of the vines to set fruit. At the base of the 
pistillate or female blossom is located the small embryonic melon 
formed before the blossom opened, and it is necessary that the pollen 
from the male flower be transferred by bees or other insects to the 
female flower* Where melons are grown in greenhouses or in closed 
frames it is essential that provision be made for the entrance of 
bees in order that the pollen be transferred . 

Peach and Nectarine 

Cullinan, F. P. 

1937. Improvement of stone fruits. II. S. Dept. Agr. Yearbook 1937: 
665-748 . 

p. 675? The nectarine was formerly thought to be a different 
species from the peach. It is now known that the nectarine is simply 
a smooth-skin peach. The trees differ in no respect from the peach, 
and it is impossible to tell a peach tree from a nectarine tree. 

p. 695: Most varieties of peaches are self-fruitful. Occasion- 
ally failure to produce crops may be due to pollen sterility, which 
is exhibited in a few commercial varieties, such as J. H. Hale, 
Halberta, Candoka, Mikado, and Chinese Cling. 

Marshall, R. E., Johnston, Stanley, Hootman, H. D., and Wells j H. M. 

1929. Pollination of orchard fruits in Michigan. Mich. Agr. Expt. Sta. 
Spec. Bui. 188, 38 pp. 

p. 29: A J. H. Hale peach orchard favorably located on the 
Friday Bros. Farm near Coloma and containing a few scattering trees 
of other varieties had produced but a few fruits since planting in 
1917. When it was learned that this variety was self -sterile, South 
Haven and Elberta trees were planted in the vacancies as pollinizers 
for the J. H. Hale. In spite of this provision the orchard produced 
less than 10 bushels of peaches in 1926. Before the succeeding blos- 
soming period. 20 colonies of bees were located in the orchard and it 
produced the first crop of fruit in 11 years . 


Kinman, C. F., and Magness, J. H. 

1940. Pear growing in the Pacific Coast States. U. S. Dept. Agr. 
Farmers 1 Bui. 1739, 38 pp. 

p. 24 t that cross-pollination is advantageous to setting fruit 
of practically all varieties is now generally conceded. Provisions 
for cross-pollination should be made, notwithstanding the fact that 
such varieties as Bartlett, Anjou, and others may, under favorable 

- 30 - 

conditions, set fair crops when -planted alone. 

One tree is considered sufficient to polliniae eight others 
if bees are provided to carry the pollen . 

Tufts, W. P., and Philp, G. L. 

1923. Pear pollination. Calif. Agr. Expt. Sta. Bui, 373, 36 pp. 

p. 35 i Pear fruits resulting from cross-pollination do not 
appear to exhibit the same tendency to fall after the June drop . 
as do those resulting from self-pollination. 

Pollinating agencies such as honey bees are necessary to set 
a good crop of fruit. 

Persimmon, Native 

Fletcher, W. F. 

1942. The native persimmon. U. S. Dept. Agr. Farmers 1 Bui. 685, 
22 pp. 

pp. 3-4 1 The trees are generally dioecious,* that is, the 
pollen-bearing and fruit- producing flowers are borne on separate 
trees. The pistillate or fruit-producing flowers are borne singly, 
whereas the staminate or pollen-bearing flowers are generally pro- 
duced in threes. The pollen is very light and powdery, and, although 
it is generally distributed by bees that frequent the trees in great 
numbers during blossoming time, it can also be carried to great 
distances by the wind. 

Plum and Prune 

Hendrickson, A. H. 

1918. The conanon honey bee as an agent in prune pollination. Calif. 
Agr. Expt. Sta. Bui. 291, pp. 215-236. 

p. 236: The results of the two seasons' work seem to warrant 
the following conclusions: Both the French and Imperial prunes may 
be aided in setting fruit by the use of bees in the orchard during 
the blossoming period, provided the trees are in a normal, healthy 

The absence of bees in the orchard may mean a low percentage of 
set with both of these varieties . 

Hendrickson, A. H. 

1922. Further experiments in plum pollination. Calif. Agr. Expt. 
Sta. Bui. 352, pp. 247-266* 

- 31 - 

p. 266: The presence of honey bees materially aided in setting 
heavy crops on the following combinations of varieties: Formosa and 
Wickson; Eeauty and Santa Rosa; Diamond and Grand Duke. Observations, 
furthermore, showed that many other combinations were also benefited 
by these insects. 

Hendrickson, A. H. 

1919. Plum pollination. Calif. Agr. Expt. Sta. Bui. 310, pp. 1-28. 

p. 27: A comparison over a number of years between trees where 
there was an abundance of bees flying and trees where bees were 
scarce, emphasized the desirability of having bees in the orchard. 
Even self-fertile varieties were immensely benefited by the presence 
of bees as an agency for distributing pollen . 

Kinman, C. F. 

1931- Plum and prune growing in the Pacific States. U. S. Dept. Agr. 
Farmers' Bui. 1372, 57 pp. 

p. 25: The presence of bees in the plum orchard at blossoming 
time has been demonstrated to be almost an economic necessity.... 
Poor crops or perhaps failures may be expected of self-sterile 
varieties where no bees are present, and even with self -fertile 
varieties the presence of bees has caused a decided increase in 
the crop . 


Darrow, G. 14. 

1937. Strawberry improvement. U. S. Dept. Agr; Yearbook 1937: 445-495 • 

p. 455: Pollen is carried by bees and other insects, but it is 
also thrown out of the stamens as the anthers crack open ... or it 
is jarred out and blown by the wind and falls on the pistils. A 
variety having perfect or hermaphrodite flowers can produce fruit 
when planted by itself, but one with pistillate flowers cannot set 
fruit unless perfect-flowered plants are nearby to furnish pollen 
through the agency of bees or other insects . 

Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 608 pp. Philadelphia. 

p. 347: Fertilization and Development of the Fruit. — Strawberries 
are protogynous, that is, the pistils of a flower mature before its 
stamens. Hence cross-fertilization is secured; and this usually by 
insects. Non-fertilization or incomplete fertilization is usually 
indicated by berries with hard, greenish, undeveloped apices, so-called 

Tung. See Almond. 

- 32 - 


Goff, C. C. 

1937. Importance of bees in the production of watermelons. Fla. Ent. 
20(2 )i 30-31. 

From these observations it is quite evident that the size of 
the melon crop may be greatly influenced by the bees. Observations 
in Florida and elsewhere show that certain days are favorable for 
setting melons while a very poor set will occur on other days, due 
to weather conditions. If the favorable days are few and the supply 
of bees small, the yield may be small. 

It is therefore important that a good set be obtained from the 
earlier flowers and to insure this an adequate supply of bees should 
be present . Thus, in certain areas at least, the earliness and size 
of yield may be increased by keeping honeybees near the field during 
the flowering season . In large fields, the best results should be 
obtained by having a hive near the center of the field. 

Seed Crops 


Tysdal, H. M. 

194.0. Is tripping necessary for seed setting in alfalfa? Amer. Soc. 
Agron. Jour. 32: 570-585. 

p. 582: One factor ... is the effect of constant visits of 
honey bees to the same flower. When the bees are extremely numerous 
the same flower may be visited a great many times, and in this way a 
higher percentage of flowers are tripped than shown in Table 10. 
Actual counts have shown honey bees to trip as much as 12 percent 
of the flowers of a given raceme during the course of two or three 
days. This would indicate that honey bees in abundance might be 
beneficial for seed setting . It has also been observed that certain 
honey bees are much more apt to trip alfalfa flowers than others, 
thus indicating rather wide differences among individuals in the 
same species. Plants also differ in ease of tripping. 

Tysdal, H. M., and Westover, H. L. 

1937. Alfalfa improvement. U. S. Dept. Agr. Yearbook 1937: 1122-1153. 

p. 1139: The ability of the honey bee (Apis melllfera L. ) to 
trip alfalfa flowers is not so easily clarified. Piper et al. found 
that honey bees tripped only from 0.3 to 4.7 percent of the flowers 
visited and many visits to the flower were required before tripping 
was effected. Dwyer ..« of Australia, has found that honey bees 
cause a considerable amount of tripping and has suggested the use of 
honey bees in cages in breeding work. Michigan workers have also 

- 33 - 

found the honey bee to be effective when confined to small area s . 
Helmbold ... states that honey bees collecting pollen cause trip- 
ping and attributes more tripping to them than to bumblebees . 


Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 606 pp. Philadelphia. 

p. 244 j Pollination. — Common asparagus is almost entirely 
insect-pollinated. The nectaries are small and concealed at the 
base of the perianth. Standnate flowers are first to open. 

Bras si ca 

Magruder, R. 

1937. Improvement in the leafy cruciferous vegetables. TT. S. Dept. 
Agr. Yearbook 1937: 283-299. 

p. 283: According to most botanists, cabbage, cauliflower , 
broccoli . green-sprouting broccoli . brussels sprouts, kale, collards , 
and kohlrabi are very closely related, being horticultural forms of 
the species Bras si ca oleracea L. 

p. 291 : By planting in alternate rows strains that are self- 
compatible but cross-fertile, hybrid seed will result through the 
action of insects in carrying the pollen from one strain to the other . 
Bud pollination of a few flower clusters of each strain results in 
enough seed to perpetuate the strains for later crops. Bees have 
been found to be very effective agents in the cross transfer of 
pollen . and by enclosing the individuals or groups of plants under 
cheesecloth cages the bees may be used in working out the problem 
of obtaining desirable crosses between different strains or increasing 
the seed of a number of desirable crosses for preliminary commercial 

wOS tS ... . 


Pearson, 0. H. 

1932. Incompatibility in broccoli and the production of seed under 

cages. Amer. Soc. Hort. Sci. Proc. 29: 468-471. 

p. 4.69: The results given here indicate that the use of small 
numbers of bees under cheesecloth cages is a possible method of pro- 
ducing small quantities of broccoli seed, if the compatibility situ- 
ation is such that seed can be produced with the pollen available. 


Leighty, C. E. 

1919. Buckwheat. U. S. Dept. Agr. Farmers 1 Bui. 1062, 24 pp. 

- 34 - 

pp. 21-22: It is not advisable to grqw buckwheat for use 
by bees alone. Commercial beekeeping in buciyheat-growing 
sections is advisable, as bees c^n make use of the flowers pro- 
duced and may in turn be of use in fertilizing the flowers . 
Many buckwheat growers, in fact, believe, that the weight per bushel 
of the seed is heavier where the crop* has 'been worked largely bv 
bees . 

White, J. W., Holben, F. J., and Richer, A. C. 

1941. Experiments with buckwheat. Fa. Agri, Expt. Sta. Bui. 403, 62 pp. 

p. 57: Buckwheat plants are a valuable, source of nectar, and 
since the common varieties are highly self-sterile, bees are of 
great value in bringing about cross-pollination. 


Pearson, 0, H. 

1932. Breeding plants of the cabbage group. Calif. Agr. Expt. Sta. 
Bui. 532, 22 op. 

pp. 4-5: Insects visit the flower ( Brassica oleracea) freely. 
Honeybees, although usually plentiful, often fail to be very effi- 
cient, because they do not work at temperatures below 60° F. 
Bumble-bees are not very plentiful in California, but usually a 
few of them are collecting pollen in nearly every field. 

p. 7: Cross-pollination which is the rule in Brassica is 
usually brought about by insect visitation . Bees are the active 
pollinating agents . 


Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 608 pp. Philadelphia. 

p. 510: The flowers are mostly insect-pollinated. 

Umbelliferea (Carrot Family) 
(Carrot, Parsnip, Celery). 

Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 608 pp. Philadelphia. 

p. 504: The umbellifers are usually insect-pollinated. 
Protandry is common. 

- 35 - 

Clover, Alsike 

Megee, C. R., and Kelty, R. H. 

1932. The influence of bees upon clover and alfalfa seed production. 
Mich. Agr. Expt. Sta. Quart. Pul. M U)t 271-277. 

p. 277: The honeybee was found to be a very effective pol- 
linating agent for June and alsike c lovers a nd for a lf alfa and the 
presence of Large_ num bers of bees result ed in marked inc reases in 
the seed crops of these le g umes . 

United States Department of Agriculture. 

1942. A much larger harvest of hay crop seeds needed in 194.2. U. S. 
Dept. Agr., Food for Freedom Program, Background Information 
Series, No. 7, 5 pp. 

p. 3: The placement of one hive of honey bees per acre adja- 
cent to or in an alsike field will "materia lly, inc rease seed pro- 
duction . 

Clover, Crimson 

Hollowell, E. A. 

1938. Crimson clover. U # S. Dept. Agr. Leaflet 160, 8 pp. 

p. 8: Crimson clover is a prolific seed-producing plant and 
yields of 5 to 10 bushels per acre are common, depending upon the 
thickness of the stand, the amount of growth that is produced, and 
the care exercised in harvesting the seed. The florets are self- 
fertile, but bees are effective in tripping and transferring the 
pollen, with a consequent in cre a se in the nu mber o f seed per hea d . 
The placing of colonies of honeybees adjacent to blooming f ields 
will effectively increase pollination . 

Clover, Ladino White 

Hollowell, E. A. 

194.2. Ladino white clover for the Northeastern States. U. S. Dept. 
Agr. Farmers' Bui. 1910, 10 pp. 

p, 10: Because cross-pollination is necessary for .seed forma- 
tion, it is advisable to move hives of honeybees adjacent to the 
fields before the plants bloom . A minimum of one hive per acre 
materially increases seed production. 

Clover, Red 

Hollowell, E. A. 

1932. Red-clover seed production in the Intermountain States. U. S. 
Dept. Agr. Leaflet 93, 7 pp. 

p. 7: The dependence of seed setting on the number and activity 
of honeybees and bumblebees is not realized by most farmers who grow 
red-clover seed. The red-clover flower is practically self-sterile; 
that is, the pollen of a flower will not fertilize any other flower 
on any head of the same plant. Therefore, before fertilization can 
occur, it is necessary that the pollen be. transf erred between flowers 
on different plants. This cr oss-polli nation is done jar inci pally by 
honeybees, bumblebees, and other kinds of bees, whose presence in 
large numbers at the time red clover is blooming is essential for 
large yields of seed. Tf other nectar and pollen Droducing plants 
more liked by the bees than red clover are available, the honeybees 
in particular will work the other plants in preference to the red- 
clover flowers. If only the second growth is saved for seed, .the 
time of cutting the first growth may be regulated so that the 
second growth will be in full bloom when other flowering olants are 
scarce and then large numbers of bees are present. There is r eason 
to believe that in sections where an I ncreas e in acreage has been 
accom panied by declin ing yields of see _d r t he introduction of additional 
colonies of honeybees would prove profitable. Bumblebee nests should 
not be destroyed, and every effort should be made to provide desirable 
nesting places for queen bumblebees. 

Fieters, A. J., and Hollowell, E. 4. 

1937. Clover improvement. U. S, Dept. Agr, Yearbook 1937: 1190-12L4. 

p. 1199: Bees visit the red clover floret for nectar and pollen 
or both, tripping the florets and transferring pollen from plant to 
plant, thus constantly maintaining the co ndition of mixed inheritance 
in the species . Other insects, such as moths, are constantly seen on 
red clover heads, but they do not come in contact with the pollen and 
therefore do not effect cross-pollination. 

There has been considerable controversy as to the extent to 
which pollination can be accomplished by honeybees. Discussion has 
centered upon the fact that the tongue of the honeybee is not long 
enough to reach the nectar. The literature on this subject is 
voluminous and cannot be reviewed here. More recent in vestigations 
clearly indicate that honeybees visit red clover principally for 
pollen and seldom obtain nectar, but regardless of what is obtained , 
pollen is transferred and cross-pollination is effected . 

- 37 - 

United States Department of Agriculture. 

19^2. A much larger harvest of hay crop seeds needed in 1942. U. S. 
Dept. Agr., Food for Freedom Program, Background Information 
Series, No. 7, 5 pp. 

p. 3s A lack of sufficient pollination insects when red 
clover is blooming is one reason for low seed yields. Honeybees . 
one of the principal pollinators of red clover, are the only kind 
that can be readily increased and moved. The placement of one 
hive of honeybees per acre adjacent to or in a red clover field 
when blooming will increase seed production . 

Clover, Strawberry 

Hollowell, E. A. 

1939. Strawberry clover. U. S. Dept. Agr, Leaflet 176, 8 pp. 

p. 6: The blossoms of strawberry clover are visited by honey- 
bees. Apparently they obtain considerable nectar, which indicates 
that this is a good honey plant. 

Clover, White 

Hollowell, E. A, 

1936. White clover. U, S. Dept. Agr. Leaflet IIP, 8 pp. 

p. 7: White clover is naturally a free-blossoming plant in 
all parts of the United States, but only in a few sections has 
seed production developed as a farm enterprise. ... Even when 
blossoms are abundant, moist, cloudy weather is unfavorable to 
bee activity, and necessary cross-pollination is, therefore, re- 
stricted and seed production reduced. The presence of colonies 
of honeybees in the immediate vicinity of clover-seed producing 
fields usually insures a maximum of cross-pollination . 


Allard, H. A. 

1910. Preliminary observations concerning natural crossing in cotton. 
Amer. Breeders' Mag. 1: 24.7-261. 

pp. 256-257: Honeybees are among the most frequent visitors 
of cotton blossoms, but, at the same time, they are very generally 
visitors of the outer involucral nectaries alone. ... Nearly all 
bee visitors show a marked tendency to pass from plant to plant 
uo and down the rows rather than across. 

p. 2581 These casual records are sufficient to show the 
enormous number of blossoms a single bee is capable of visiting 

- 38 - 

in a few hours, and the probabilities of intercrossing a great 
number of these all over the field. Almost before day, bees 
are forcing their way into the expanding buds, and an examina- 
tion of these reveals many whose stigmas have been pollinated 
long before the flowers are fully opened. The writer has 
observed that in the near vicinity of domestic hives in 
northern Georgia the number of honeybee visitors is enormously 

p. 261: In cotton fields of northern Georgia the demonstrated 
proportion of crossed blossoms is at least 20 per cent, with strong 
probabilities that approximately 4-0 per cent of the blossoms are 
crossed. Although crossing may be very detrimental in unselected 
cotton, in selected cotton it is probably beneficial. 

Kearney, T. H. 

1923. Self-fertilization and cross-fertilization in Pima cotton. 
U. S. Dept. Agr. Dept. Bui. 1134, 68 pp. 

p. 36: There is little doubt that natural cross-pollination 
in cotton is effected almost solely by the agency of insects. The 
nature of the pollen grains of Gossypium is unfavorable to their 
transportation by currents of air. 

p. 37 j Various Hymenoptera are the most efficient carriers 
of cotton pollen at Sacaton, Ariz,, as is probably the case wherever 
cotton is grown. The honeybee and the wild bees (Melissodes spp.) 
are the most important cotton pollinators in this locality . 

The honeybee ( Apis mellifica L .) is very assiduous in its 
visits to cotton flowers, although sometimes preferring the extra- 
floral nectaries to- those with the flower. Nevertheless, this 
insect probably holds first rank at Sacaton. Ariz., as a conveyor 
of cotton pollen, especially among Pima flowers. As was noted on 
a preceding page, honeybees entering and emerging from the flowers 
when the petals are just beginning to unfold almost invariably come 
in contact with the reproductive organs. 

Meade, R. M. 

1918. Bee keeping may increase the cotton crop. Jour. Hered. 9: 282- 

p. 285: No effort was made to exclude insects, and the weather- 
conditions during the course of the investigation were not unfavorable 
to their activities. It is evident from the increased yield of bolls 
secured in the long-pistiled Durango vari ety through artificial polli- 
nation that the presence of additional pollinating insects would aid 
in reducing the high percentage of shedding. The value of honey 


- 39 - 

bees in this connection is recognized in some localities, and It 
would seem that growers of long stapled varieties might find bee- 
keeping a distinct advantage to the cotton crop . 

Cruciferous Root Vegetables 

Poole, C. F. 

1937. Improving the root vegetables. U. S. Dept. Agr. Yearbook 1937: 

p. 310: The cruciferous root vegetables — turnips, rutabagas . 
and radishes— have relatively large flowers, which are insect-polli- 
nated . 


Jones, H. A* 

1937. Onion improvement. U. S. Dept. Agr. Yearbook 1937: 233-250. 

p. 239* Most of the pollen is shed between 9 a.m. and 5 p.m. 
Pollination is effected mainly by insects that go from flower to 
flower and visit the nectaries at the base of the three inner 
stamens . Interpollination among flowers of the same umbel is no 
.doubt of frequent occurrence, as the same insect has been observed 
to visit many flowers on an umbel before leaving. In the onion, 
however, cross-pollination is the rule. 


Odland, M. L., and Porter, A. N. 

1941. A study of natural crossing in peppers ( Capsicum frutescens ). 
Amer. Soc. Hort. Sci. Proc. 38: 585-582, tables. 

p. 588: The pepper flower is rather inconspicuous and non- 
• fragrant, a fact that would suggest pollination not very likely. 
Erwin . . . found that the flowers produced nectar and that insects 
did at times visit them. The writers are of the opinion that honey 
bees are largely responsible for the cross pollination that takes 
place . This insect has been found working on the pepper plant 
rather often. The presence of the bee is rather spasmodic, however . 
as they are found only on certain warm bright days. The presence of 
bees in the vicinity may have a bearing on the amount of cross polli- 
nation . 

r, Li at. Flax 

Gubin, A. P. 

1945. Cross pollination of fibre flax. Bee World. 26:30-31. 

p. 30: Among all insects which pollinate flax flowers the 
honeybee occupies a significant place ... . The honeybee constitutes 
93.8 percent of all such insects. 

- 40 - 

p. 31 J Cross-pollination of flax by bees increased the 
yield, as measured by quantity of grain, 28.57 percent; as 
measured by weight of seed, 31.01 percent and raised the abso- 
lute weight of 1000 grains from 5.0372 to 5.1329 gm. Consequently, 
the development of seeds with se]f -pollination proved to be some- 
what depressed. Usually with a smaller quantity of seed and fruit 
they grow larger in size; in the given case the reverse was observed — 
the resultant yield with cross-pollination was higher in respect 
of both -quantity and quality. 

On the open plot where the number of visits was only 67.8 
percent of the number of flowers, the increase of the yield of 
flax proved to be less significant; the number of grains from 
500 bolls rose from 2688 to 3050, that is 13.47 percent; their 
weight rose from 13.5934 to 15.8878 gm. or 16.88 percent; the 
weight of 1000 grains rose from 5.0576 to 5.2095 gm. 


Crane, U. B., and Mather, K. 

1943. The natural cross-pollination of crop plants with particular 
reference to the radish. Ann. Appl. Biol. 30: 301-308. 

p. 307: As the radish is self-incompatible each plant must 
receive pollen from another plant to produce seed. In these experi- 
ments the pollen could come from a sister plant of the same variety 
or from a plant of a different variety. As shown in Figs. 4-6, 
25 hives of bees were maintained close to the experiments. Thus, 
the bee population was much higher than in most cases where crops 
are grown commercially for seed, and the number of bees visiting 
the plots during the flowering period was extremely large. The 
seed crop was heavy throughout the plots, indicating that cross- 
pollination had been effectively carried out. 

Kremer, J. C. 

1945. Influence of honey bee habits on radish seed yield. Mich. Agr. 
Expt. Sta. Quart. Bui. 27: 413-420, illus. 

p. 419: Figure 4 illustrates a typical example of the effective 
radius of commercial bee yards located in a radish seed area, where 
radish seed fields were located without regard or knowledge of their 

All the fields located within the circles or the 2-mile radius 
produced from 400 to 450 pounds of seed per acre, while those on 
the border of this radius or beyond averaged 200 to 300 pounds of 
seed per acre. One field located within the flying radius of two 
of these bee yards averaged 600 pounds per acre. No other colonies 

- 41 - 

of bees were known to exist in this area, though possibly there 
were some wild swarms present. 


Rudnev, V. Z. 

194-1. [The effect of pollination by bees on yield of sunflower seeds.] 
Soc. Zern. Hoz. No. 2. 134-4.0. [Abstract in Imp. Pur. 
Pastures and Forage Crops, Herbage Abs . 14-:55-56, 194-4.] 

p. 55: Field tests with % sunflower plants, which were either 
completely or partially covered with gauze to prevent pollination 
by the bees, indicated that percentage of settings was 77.7 to 
85. 9 in the insect-pollinated and 25.0 to 25.7 in the self-polli- 
nated flowers. Trials in field conditions (when a number of bee- 
hives was placed at varying distances from several observation 
plots 100 ra each in a large sunflower plantation) showed that, 
with the increase from 500 to 1250 m. of the distance of a beehive 
from the plantation, the number of bees visiting each plot daily 
fell from 100 to 61, the weight of ripe seeds dropped from 6,000 
to 3,700 grm., and the weight of empty seeds rose from 110 to 200 


Posters, A. J., and Hollowell, E. A. 

1937. Clover improvement. U. S. Dept. Agr. Yearbook 1937: 1190-1214. 

p. 1207: Pollination o f sweetclover under natura l con ditions 
is effected principally by honeybees, except insofar as the 
species, varieties, or individuals are spontaneously self-fertilized. 

United States Department of Agriculture. 

194-2. A much larger harvest of hay crop seeds needed in 1942. U. S. 
Dept. Agr. Food for Freedom Program, Background Information Series, 
No. 7, 5 pp. 

p. 3s ... lack of sufficient pollination lowers seed yields. 
Honeybees are the most valuable pol l inators . A minimum of one 
hive of honeybees per acre located close to a blossoming field 
of sweet clover will increase the quantity of seed set. 


McKee, R., and Schoth, H. A. 

194-1. Birdsfoot trefoil and big trefoil. U. S. Dept. Agr. Cir. 625, 
13 pp. 

p. 5: The general conclusion of investigators who have studieu 
seed setting in Lotus species is that both birdsfoot trefoil and 
big trefoil are practically self-sterile. Silow ... who has more 


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recently given the subject consideration draws the following con- 
clusion : 

" Lotus corn i culatus is practically self-sterile, 
bat occasional plants set a few se^Ha after self-polli- 
nation. Plants of L. major Smith (= L_j_ uliginosus Schk.) 
are, on the whole, incapable of spontaneous self-polli- 
nation, but after artificial self-pollination practically 
all plants are self-fertile, some to a very high degree. 
Thus these two perennial species are almost entirely de- 
pendent upon insect visitors for see d formation . " 

Vetches (Vicia) 

Schelhorn, K. 

194-2. Blutenbiologische Studien an der Zottelwicke. Pflanzenbau. 
IS: 311-320. 

Hungarian ( Vicia pannonica ) and hairy vetch (V. villosa ) . 
were screened to exclude bees. In the former 38 percent of the 
flowers produced seed but only 3.5 percent of the latter. Hairy 
vetch was found to be self -fertile but to require bees to transfer 
the pollen. The author concluded that seed production in hairy 
vetch is almost entirely dependent on the visits of bees to effect 
the transfer of pollen. [Abstracted from translation by Carlo Zeimet.] 

Vici a villosa 
(Hairy, Hungarian, Russian, Siberian, or Villous Vetch) 

Robbins, W. W. 

1931. The botany of crop plants. Ed. 3, 608 pp. 

pp. 4-11-412: There are five to eight pairs of leaflets, 
and many (about thirty) violet-blue, rarely white, flowers in 
one-sided racemes. Cross-fertilization is necessary for +he 
normal production of seeds. Bees are the chief agents in the 
dissemination of pollen.